Think haunted houses on Earth are scary?

HD 189733b

Do you smell something funny? Methane might be best-known for the fact that a lot of it comes from cow burps and sewage, but in higher concentrations, it’s no laughing matter.

Not only is methane a potent greenhouse gas, but it’s also poisonous, causing suffocation, vomiting, and other flu-like symptoms. Farm workers on Earth have been killed by large amounts of methane escaping tanks used to store livestock excrement.

Astronauts trying to visit the gas giant exoplanet HD 189733b would be advised to bring plenty of oxygen, as the abundance of methane and other poisonous gasses, like carbon monoxide, in its atmosphere would otherwise cause a quick death due to suffocation.

HD 149026b

How hot is HD 149026b? Let’s just say that instead of water vapor clouds, this planet has clouds made out of the vapor of heavy metals like titanium - metals that got so hot, they didn’t just melt, they vaporized. A three-day orbit puts this planet ridiculously close to its star and causes temperatures so hot that the planet’s atmosphere is burnt pitch-black, making it one of the darkest exoplanets ever discovered.

After experiencing the 4,000-degree heat of HD 149026b, you might want to find a place to cool off, like a blast furnace or bonfire, both of which are half the temperature of the average day on this hellish exoplanet.

So what might happen to the intrepid astronaut who manages to get all the way out to HD 149026b? Without the proper protection, they’d quickly be turned to charcoal, as the planet is twice as hot as incinerators used to cremate human bodies on Earth.

PSR B1257+12B

The planetary equivalent to living inside an airport X-ray machine, these small, rocky planets are bathed in high-energy radiation from their dead host star every 6.22 milliseconds. Some of the weirdest stars in existence, pulsars are incredibly dense star corpses that beam massive amounts of radiation at precisely timed intervals.

Being up-close and personal to that beam of radiation makes pulsar planets like PSR B1257+12B incredibly dangerous places to be. The gamma and X-rays that pulsars emit rip straight through human flesh and organ tissue, damaging DNA and killing cells.

Astronauts visiting a pulsar planet without proper protection would quickly find themselves experiencing the excruciating symptoms of radiation sickness: burns, vomiting, seizures, headaches, and difficulty thinking clearly, followed by death within hours. Even those who managed to survive the initial onslaught could be afflicted with radiation-caused cancer later in life.

Kepler-7 b

Kepler-7 b sounds harmless enough – one of the least-dense exoplanets ever discovered, it has a density similar to that of Styrofoam, meaning that despite its massive size, the planet would float in a tub of water.

But a parachute ride down to the core of Kepler-7 b, if it indeed has one, would be a one-way trip. Astronauts equipped to survive intense cold at the outer layers of the atmosphere and winds whipping along at hundreds of miles per hour would find themselves descending into a dark, hot abyss, with atmospheric pressures millions of times more intense than they are on Earth.

The mounting pressure would crush spaceships like empty soda cans and cause normally non-toxic gases in an astronaut’s air supply, like nitrogen and oxygen, to be so dense that they become poisonous. The force of the atmosphere would collapse an astronaut’s lungs and make it impossible to breathe, causing death from suffocation long before the drifting corpse was incinerated by internal temperatures as hot as the surface of the sun.